1. Field of the Invention
The present invention relates generally to a process for producing a cast article having a hollow cavity, and more particularly to a process for producing a hollow cast article having a desired interior contour defined by a very smooth inner wall surface.
2. Related Art Statement
A core mold has conventionally used in the prior art casting process for producing a hollow cast article having an interior cavity surrounded by a smooth inner wall surface, particularly when the interior cavity has a complicated contour. In case where it is desired that the cast product has an extremely smooth inner wall surface defining the interior cavity, a ceramic mold has been hitherto been used as the core mold. In general, such a core mold is prepared initially by molding a green core mold from a mixture of an aggregate, such as alumina or zirconia, and a binder, such as ethyl silicate, and then baking the green core mold. However, it is difficult to prepare a baked core mold of precise dimension, since the green material therefor tends to shrink or expand during the baking step to loose its dimensional stability. Other problems of the conventional ceramic core mold are that the quality thereof becomes often irregular and that the production efficiency thereof is inferior leading to high production cost.